In article , Jeff Thies wrote:
On 4/11/2011 11:25 AM, Smitty Two wrote:
In ,
Jeff wrote:

My first encounter with you

Jeff, since you don't hang out on s.e.r., I'll clue you in about Phil.
Regardless of what he knows or doesn't know, he calls everyone a
****wit, and worse, all the time. Virtually every sentence of every post
is chock full of derision. If you choose to dialogue with him, you'll
get great heaping portions of his demented abuse. So don't take it
personally.

Thanks. That's about what I surmised. A North American version of Rod
Speed.

I think Rod Speed is much worse. Meanwhile, it appears to me in my
experience in s.e.d. that P.A. is, like R.S., an Aussie.
--
- Don Klipstein )

In article , Steve Turner wrote:
A continuation of the "Why does the 115V-24V transformer keep blowing on
my Trane XB80?" discussion I started on 04/02/2011.

Yep, My A/C unit blew another transformer. SNIP from here

This one is a grasp at a straw. Was a magnet stuck on the transformer
at the time that it blew?

I realize that not too many people run transformers with magnets stuck
to them. But doing that does make their cores more prone to saturation.
--
- Don Klipstein )

In article , Phil Allison wrote:

"Don Klipstein"

Then again, I doubt a voltage spike lasting long enough to burn out a
transformer will be absorbed by a 1 uF cap across a 120V AC line.

** You missed the point entirely.

A voltage spike ( or a series of them) can easily cause insulation failure
in the enamel winding wire of the primary - then the energy to explode
the lead in and lead out wires comes from the 120 volt AC supply.

Is the O.P. having other things in his house blowing from voltage spikes
severe enough to blow transformer primary winding insulation?

I have seen lots of things blow from line voltage surges, but no
transformers indoors blowing when line voltage spikes blow other things.

My experience is that usual 120V-primary step-down transformers can
produce pulses of 2 kilovolts when used on pulses in reverse. In fact, I
have done that with about 8 different transformers dozens of times each,
and none of them lost their ability to do that. (I am aware of line
voltage spikes being noted to get even higher.)

There is also the issue of line voltage surges not easily being loaded
down by capacitors for whatever reason. I have experience with them
blowing things that had capacitors, including a CFL that had probably a 22
or 47 uF capacitor across the output of its internal bridge rectifier as
they usually do. No transformer failures in the same house from the same
event, though there were electronics failures.

The usual solutions to absorb line voltage spikes are MOVs and other
devices that absorb voltage surges by becoming conductive in response to
excessive voltage.

--
- Don Klipstein )

"Don Klipstein"
Phil Allison wrote:
"Don Klipstein"

Then again, I doubt a voltage spike lasting long enough to burn out a
transformer will be absorbed by a 1 uF cap across a 120V AC line.

** You missed the point entirely.

A voltage spike ( or a series of them) can easily cause insulation failure
in the enamel winding wire of the primary - then the energy to explode
the lead in and lead out wires comes from the 120 volt AC supply.

Is the O.P. having other things in his house blowing from voltage spikes
severe enough to blow transformer primary winding insulation?


** Totally irrelevant.

The furnace unit and the transformer in question are all we are discussing.

You have clearly not bothered to read my first or my other posts in this
thread.

Eg:

" High voltage spikes on the primary could also cause insulation failure
leading to the damage seen in the pics - lightning does this sort of thing.
So also could back emfs from the blower fan if the is a bad connection in
the AC supply feed."

Whenever AC power to that furnace is disconnected, the blower fan will
deliver a back emf spike - meanwhile that poor, little tranny is wired in
parallel with it. Other devices in the house are NOT involved.

Most AC supply transformers can tolerate repeated 2kV spikes on the primary
till the cows come home - but a badly wound one cannot. This is a specific
and fairly recent problem with small transformers made in China and
elsewhere in Asia where the makers are not fully aware of the issue of
insulation failure in the enamel windings.

Once there is a layer to layer insulation failure ( between adjacent wires)
in the primary of that tranny - the AC current draw will jump up to many
amps and may cause the feed in and out wires to explode - as seen in the
pics.

If the spike voltage is suppressed, the tranny will likely survive.

A 1uF cap provides a low impedance path for such a back emf spike, virtually
shorting it out.

OTOH a varistor provides no conduction path until its breakdown voltage is
exceeded, but is also a means of suppressing the spike voltage to a safe
value.


..... Phil

Tony Miklos wrote:
On 4/9/2011 10:06 PM, John Robertson wrote:
Steve Turner wrote:
On 4/9/2011 7:29 PM, Jim Yanik wrote:
wrote in
m:

"Steve Turner" wrote in message ...

A continuation of the "Why does the 115V-24V transformer keep
blowing on my Trane XB80?" discussion I started on 04/02/2011.

Yep, My A/C unit blew another transformer. Pictures (and wiring
diagram) he

http://www.flickr.com/photos/bbqboye...7626457562742/

Trane's manual for the unit is here (for perhaps better viewing of
the wiring diagrams that I also copied to my above flickr site as
jpg images):



http://www.trane.com/webcache/un/fur...oduct/22-1666-

07_04012009.pdf

As you can probably see in the pictures, there is visible charring
of the 115V leads going into the transformer, and of course the 115V
circuit is open (again). If you didn't see my first thread, this is
the third transformer the unit has blown. In the previous
discussion, it was discussed that perhaps the first one just blew
because of old age (6 years), and the second blew because it wasn't
a proper replacement (poor quality, made in China, etc.). This
third unit is most certainly a proper replacement, and it's most
certainly indicative of a real problem I have somewhere else in the
unit. I didn't see any such charring on the previous two units, at
least not like this.

I never got a real chance to test out the system after installing
this third transformer. We had cool weather for several days, and I
never tried to force the system to come on so I could monitor it;
that was probably a mistake. Unfortunately, I was also absent from
the premises during the extended times when the unit was most likely
operational, so that didn't help either. However, my family tells me
that it WAS working and cooling the house rather nicely, for at
least a day, perhaps two. I'm getting 115V in all the right places,
so it doesn't look like an over-voltage condition to me. Perhaps
it's an overheating condition? It looks to me like the only real
load on this circuit is the blower motor; could the motor be causing
this? The blower spins freely when I turn it by hand. Start
capacitor on the motor maybe? Relay on the control board perhaps?

a bad start cap would not affect the 24v control transformer,that just
powers the controller board and relays.
either something is loading the transformer or a problem with input
voltage.


Just a thought,

When you put the new transformer in does the "Diagnostic Light" LED
turn on ?
Does the LED blink or flash in one of the patterns indicated in the
"diagnostic codes" section that you posted a link to ?

The "diagnostic codes" imply that the control board can detect
several of the problems mentioned by others.
Maybe a good starting point as there is not enough time to test with
test equipment.

robb



a line voltage monitor may be needed to see if there's some short-term
overvoltage applied to the transformer,and a oscilloscope may
determine if
the input waveform is sinusoidal or otherwise,because 60hz iron core
tranformers don't like extreme distortion on their input,it gets
converted
to heat,not output voltage. a DMM will not show line distortion or
short
term overvoltages.
are the wires burned close to the transformer,or over their entire
length?

I peeled the insulation back from the hot and neutral wires and the
burning only occurred right at the terminals, no more than 1/4" into
the wiring.


So the problem is the joint of the transformer wiring to the lugs. They
may have cold solder joints, or the lug may be slightly loose - enough
to crack the solder connection over time. Your transformer may still be
good!

When you are examining the transformer wire make sure it is stripped
enough to get good solder coverage. Burn off the insulation (enamel) -
do not sand, scrape, or try to erode it because if you scratch the wire
it will break at the scratch.

Re-solder the transformer connectors after first making sure the wire
has at least two complete wraps around the solder lug and the solder
makes a good meniscus joint to the wire and lug. Also use a good grade
of solder, not regular 60/40, find some 63/37 solder (Kester is best) -
this solder resists cold solder joints due to movement when cooling by
solidifying very fast.

John :-#)#

Hi John, fancy meeting you here! Wait, I didn't realize this is cross
posted to sci.electronics.repair Now I know why you are here. Glad you
liked the package.

Tony

Hi Tony,

Yes, we enjoyed the peanut brittle...

I do not think the original poster noticed my suggestion above, that
failure mode is really not going to be too much load or some weird AC
situation - it's either a short to the metal case the transformer is
mounted in or a problem with the wire to solder lug joint.

Would be nice to know if that idea was checked out...

John :-#)#

--
(Please post followups or tech enquiries to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

On Mon, 11 Apr 2011 15:48:43 +1000, "Phil Allison"
wrote:




** The primary appears to be EXPLODING !!

You ridiculous ******.

Phil - your mamma should wash your mouth out with soap.


** You need to get your hands off of it.


I SAID the other two scenarios were long shots ..

** And I said they were ridiculous drivel.

- but so is everything else that has been suggested.

** Your opinion is based on your ignorance only.

The windings of the trasnformer do not
APPEAR to be overheated - looks like just blackened at the connections
between the winding and the connecting wires.


** See the vaporised metal coating deposited on the plastic cover next to
the tranny?

That is a damn EXPLOSION !!

It happened very suddenly and made a loud bang too.

I said:

" High voltage spikes on the primary could also cause insulation failure
leading to the damage seen in the pics - lightning does this sort of thing.
So also could back emfs from the blower fan if the is a bad connection in
the AC supply feed."

If the insulation on the enamel wire of the primary is punctured by a HIGH
VOLTAGE SPIKE, effectively shorting out most of the primary - then the
120 AC supply ( no fuse exists remember ) will easily turn the two exposed
wire ends into metal vapour !!!

Cos they just became the fuses.

It just so happens that many small transformers made in China, India & Sri
Lanka etc are very prone to this sort of failure - due to bad manufacturing
practices.



.... Phil


So you are agreeing with what I said before - most likely problem is
cheap crap component.

We can be relatively sure it wasn't lightning 3 times.
If the back emf from the motor is causing the problem, the bad
connection to the motor should have made itself VERY evident by now.
Not saying it is NOT part of the problem - like you, I wasn't there
watching it fail - and neither you nor I heard the noise you speak of.

And IF the problem is what you say it is (and I'm not saying it is
not), then probing the old primary and getting to the winding beyond
where the solder joint "exploded" you should be able to measure a
significantly lower than normal primary resistance.

That measurement has not, as far as I know, been made and reported.

If it was mine, or if I had the transformer at hand, I'd have it apart
and analysed in no time. If the primary is shorted, I'd know, within
an hour or two of the failure..
And with that second primary, it would not be hard to determine if the
110 volt primary is shorted without even dissassembling the
transformer..

At this point no-one has actually posted FOR SURE what the primary
configuration is. Is it a mult-tapped primary, set for 115, 208, and
230 volts, or is it 2 independent primaries, or is it 2 primaries that
need to be connected either in series or parallel depending on the
voltage (115 or 230)

I don't know this, and you don't know either unless you are
clairvoyant, because it has not, to this point, been established and
reported.

So we are all guilty of the same thing - making ASSumptions.

On Mon, 11 Apr 2011 09:27:43 -0400, Tony Miklos
wrote:

On 4/11/2011 12:59 AM, wrote:
On Sun, 10 Apr 2011 00:18:44 -0400, Jeff
wrote:

On 4/9/2011 9:41 PM, wrote:
On Sat, 09 Apr 2011 19:22:57 -0400, Jeff
wrote:



But first do as I suggested in another thread,look carefully for
anything burnt and check the polarity of the line. Make sure the neutral
is neutral. You can measure from the ground prong. See the note in the
schematic. I'm not so sure this didn't arc to the transformer shell,
from looking at the pic. You may wish to measure voltage (AC) from the
transformer shell to a guaranteed neutral.

It's AC so there is no polarity. It's single output, non grounded, so
it doesnt matter which direction either the primary or secondary are
connected. Good to have the white on neutral and the bloack on live,
but it will have NO EFFECT on the operation. - or the life of the
transformer.


Except that the schematic has a note at the top that says:

Important
Integrated Control is polarity sensitive.
Hot leg of 120V power supply must be connected to the black power lead...

Whats with that?


I'm sure I am as baffled by that as you are. AC in not "polarity
sensitive" and as long as neither side of the primary or secondary is
grounded the control should not know which way the primary (or
secondary) is connected..

I have a guess, maybe the board has to be in sync with another power
source. Would reversed polarity make it 180º out of sync?
Does not APPEAR to be another power source - - -

On 4/11/2011 4:37 PM Stormin Mormon spake thus:

OK, that makes a bit of sense. Seems like a bit of bother
for what you can track down, with a VOM and some common
sense.

As usual, being an ignoramus, you completely miss the point.

The light bulb not only allows you to detect if there's a short causing
too high a current draw, but it also *saves the device under test* from
releasing the magic smoke if there is such a smoke.

If you use some other method of measuring current--break circuit and
insert ammeter, or use clamp-on-meter, the meter will tell you there's a
short, all right, at about the same time the transformer erupts in a
ball of smoke and fire.


--
The current state of literacy in our advanced civilization:

yo
wassup
nuttin
wan2 hang
k
where
here
k
l8tr
by

- from Usenet (what's *that*?)

On Tue, 12 Apr 2011 00:12:48 +0000 (UTC), (Don
Klipstein) wrote:

In article , Jeff Thies wrote:
On 4/11/2011 11:25 AM, Smitty Two wrote:
In ,
Jeff wrote:

My first encounter with you

Jeff, since you don't hang out on s.e.r., I'll clue you in about Phil.
Regardless of what he knows or doesn't know, he calls everyone a
****wit, and worse, all the time. Virtually every sentence of every post
is chock full of derision. If you choose to dialogue with him, you'll
get great heaping portions of his demented abuse. So don't take it
personally.

Thanks. That's about what I surmised. A North American version of Rod
Speed.

I think Rod Speed is much worse. Meanwhile, it appears to me in my
experience in s.e.d. that P.A. is, like R.S., an Aussie.
That would go a long ways to explaining his potty mouth.

If the back emf from the motor is causing the problem, the bad
connection to the motor should have made itself VERY evident by now.

** Not true at all.


If it was mine, or if I had the transformer at hand, I'd have it apart
and analysed in no time. If the primary is shorted, I'd know, within
an hour or two of the failure..


** What is clear is that the primary has suddenly drawn a very large current
and that means there are SHORTED turns inside the primary.

Go away ******.


...... Phil

I have to agree with Don. DC power component on secondary OR primary,

** You are both wrong.

or not connected right are the 2 most likely problems after "cheap
crap component"

** Which is no help to the OP.



..... Phil

On 4/11/2011 10:01 PM, wrote:
On Tue, 12 Apr 2011 00:12:48 +0000 (UTC), (Don
Klipstein) wrote:

In , Jeff Thies wrote:
On 4/11/2011 11:25 AM, Smitty Two wrote:
In ,
Jeff wrote:

My first encounter with you

Jeff, since you don't hang out on s.e.r., I'll clue you in about Phil.
Regardless of what he knows or doesn't know, he calls everyone a
****wit, and worse, all the time. Virtually every sentence of every post
is chock full of derision. If you choose to dialogue with him, you'll
get great heaping portions of his demented abuse. So don't take it
personally.

Thanks. That's about what I surmised. A North American version of Rod
Speed.

I think Rod Speed is much worse. Meanwhile, it appears to me in my
experience in s.e.d. that P.A. is, like R.S., an Aussie.
That would go a long ways to explaining his potty mouth.

Perhaps that goes all the way. Hey, I learned something about Oz today.
Funny the guys from NZ I know seem quite nice. I suppose it was a surly
lot they are descended from... or is it the climate? No matter.

Jeff

In article , Phil Allison wrote:

"Don Klipstein"
Phil Allison wrote:
"Don Klipstein"

Then again, I doubt a voltage spike lasting long enough to burn out a
transformer will be absorbed by a 1 uF cap across a 120V AC line.

** You missed the point entirely.

A voltage spike ( or a series of them) can easily cause insulation failure
in the enamel winding wire of the primary - then the energy to explode
the lead in and lead out wires comes from the 120 volt AC supply.

Is the O.P. having other things in his house blowing from voltage spikes
severe enough to blow transformer primary winding insulation?

** Totally irrelevant.

The furnace unit and the transformer in question are all we are discussing.

You have clearly not bothered to read my first or my other posts in this
thread.

Eg:

" High voltage spikes on the primary could also cause insulation failure
leading to the damage seen in the pics - lightning does this sort of thing.

Why would that be, in your words, "totally irrelevant" to whether or not
the O.P. had any electrical/electronic failures elsewhere in his home
attributable to voltage surges?

As opposed to 3 transformers blowing in the same appliance with nothing
else anywhere in the home running into trouble from voltage surges?

While I have experienced roughly 8 transformers surviving repeated
abusive pulse-in-reverse-direction developing about 2 KV across the
primary without any degradation against ability to do so?

So also could back emfs from the blower fan if the is a bad connection in
the AC supply feed."

Whenever AC power to that furnace is disconnected, the blower fan will
deliver a back emf spike - meanwhile that poor, little tranny is wired in
parallel with it. Other devices in the house are NOT involved.

Why would the solution be deploying a capacitor, rather than repairing
the poor connection or deploying a voltage-dependent spike-absorbing
device such as an MOV?

Most AC supply transformers can tolerate repeated 2kV spikes on the primary
till the cows come home - but a badly wound one cannot. This is a specific
and fairly recent problem with small transformers made in China and
elsewhere in Asia where the makers are not fully aware of the issue of
insulation failure in the enamel windings.

So, why should we hear about problems about that from only one customer
blowing 3 of them?

Once there is a layer to layer insulation failure ( between adjacent wires)
in the primary of that tranny - the AC current draw will jump up to many
amps and may cause the feed in and out wires to explode - as seen in the
pics.

If the spike voltage is suppressed, the tranny will likely survive.

A 1uF cap provides a low impedance path for such a back emf spike, virtually
shorting it out.

Why should 1 uF protect the trannies in question while 22-47 uF fails to
protect a compact fluorescent lamp from a line voltage surge that blows
even other electronics in 2 houses but did not blow any in-home trannies?

OTOH a varistor provides no conduction path until its breakdown voltage is
exceeded, but is also a means of suppressing the spike voltage to a safe
value.

Certainly protects against applying for even a microsecond more than
roughly 250-300 volts across transformer primaries, where it appears to me
that we agree that transformer primaries usually survive 2,000 volts pulse
voltage?

I seem to think that the trannies are probably blowing from either
improper wiring (connecting only 1 of the 2 primary winding sections
possibly noted for 120V usage), or from secondary load malfunction
including bridge rectifier failure in manner of a diode "failing open".

Or, extreme-oddball trouble such as sticking a magnet to the tranny.
But that's grasping-at-straws, like line voltage irregularities that blow
3 trannies in 1 piece of equipment but draw no other complaints such as
blowing of electronics downstream of the tranny in question, or elsewhere
in the house where one appliance blew 3 trannies.
--
- Don )

"Don Klipstein the Troll"

Why would that be, in your words, "totally irrelevant"

** You posted under my words and it was not relevant to them.


Why would the solution be deploying a capacitor, rather than repairing
the poor connection or deploying a voltage-dependent spike-absorbing
device such as an MOV?

** A suitable MOV is also a possible solution.

You still have not read all my posts in this thread.


So, why should we hear about problems about that from only one customer
blowing 3 of them?

** Stop making silly stuff up - you pathetic ******.


Why should 1 uF protect the trannies in question ...

** Already answered.

( snip bull**** story)

Keep on ignoring the evidence in the photos and you will never get close to
what sort of failure has occurred.

Facts are just like water off a ducks back to you - Don.

Co you fools like you believe whatever they ****ing feel like.



..... Phil

In article , Phil Allison wrote:



I have to agree with Don. DC power component on secondary OR primary,

** You are both wrong.

or not connected right are the 2 most likely problems after "cheap
crap component"

** Which is no help to the OP.

Please add helpfulness, as opposed to adding nothing but saying who
is wrong.

I chimed in explaining stuff every time. At this point that I respond
to, you are doing nothing but claiming who is wrong.

It appears to me, posting nothing but who is wrong is even lower than
my grasping-at-straws bit of any magnets on the transformer in question.

--
- Don Klipstein )

In article , Phil Allison wrote:

"Don Klipstein the Troll"

Why would that be, in your words, "totally irrelevant"

** You posted under my words and it was not relevant to them.

You snipped the relevance.

Why would the solution be deploying a capacitor, rather than repairing
the poor connection or deploying a voltage-dependent spike-absorbing
device such as an MOV?

** A suitable MOV is also a possible solution.

So, why should I get merely "also a possible solution" after part
numbers for capacitor part numbers were digged up?

You still have not read all my posts in this thread.

I have endured doing that, though I prefer to not waste time at
contaminating Usenet with wasting time to responding to even the posts of
yours that I don't find deserving a response.

So, why should we hear about problems about that from only one customer
blowing 3 of them?

** Stop making silly stuff up - you pathetic ******.

Do you claim that the transformer customer blew fewer than 3? Do you
claim that the disappointed transformer customer is not alone?

If so, post support to your claims!

Why should 1 uF protect the trannies in question ...

** Already answered.

( snip bull**** story)

Keep on ignoring the evidence in the photos and you will never get close to
what sort of failure has occurred.

However, it was already explained to me clearly that the photo'ed tranny
showed charring evidence of severe primary overcurrent. What do you
expect to gain from me, or against me, if I take the time to look at the
photos that this thread gave me graphic descriptions of?

Facts are just like water off a ducks back to you - Don.

Co you fools like you believe whatever they ****ing feel like.
--
- Don )

"Don Klipstein = one Looney Troll"

Why would that be, in your words, "totally irrelevant"

** You posted under my words and it was not relevant to them.

You snipped the relevance.

** Blatant lie #1.


Why would the solution be deploying a capacitor, rather than repairing
the poor connection or deploying a voltage-dependent spike-absorbing
device such as an MOV?

** A suitable MOV is also a possible solution.

So, why should I get merely "also a possible solution" after part
numbers for capacitor part numbers were digged up?

** Wot brain dead drivel.


You still have not read all my posts in this thread.

I have endured doing that,

** Blatant lie #2.


So, why should we hear about problems about that from only one customer
blowing 3 of them?

** Stop making silly stuff up - you pathetic ******.

Do you claim that the transformer customer blew fewer than 3? Do you
claim that the disappointed transformer customer is not alone?

** More brain dead drivel.

Don is right off with the fairies and pixies and TROLLS.


Keep on ignoring the evidence in the photos and you will never get close
to
what sort of failure has occurred.

However, it was already explained to me clearly that the photo'ed tranny
showed charring evidence of severe primary overcurrent.

** Nothing you have posted explains that fact at all.

Got a ****ing clue how much current it takes to vaporise copper wires like
that ?

Obviously ****ing not.

Facts are just like water off a duck's back to you - Don.

Cos ****wits like you believe whatever they ****ing feel like.


FOAD

- you useless, autistic, PITA turd.



..... Phil

"Don Klipstein"


** FOAD - you stupid, ridiculous arsehole.

There you go, again. Completely mistaken about what I'd
reccomend in the way of diagnostic. Just making up garbage,
and then trying to assign it to me. Well, you should do that
more often. Then, everyone can see what your true character
is like. Please write often, and lengthy. The more you
write, the better I look.

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


"David Nebenzahl" wrote in message
s.com...
On 4/11/2011 4:37 PM Stormin Mormon spake thus:

OK, that makes a bit of sense. Seems like a bit of bother
for what you can track down, with a VOM and some common
sense.

As usual, being an ignoramus, you completely miss the point.

The light bulb not only allows you to detect if there's a
short causing
too high a current draw, but it also *saves the device under
test* from
releasing the magic smoke if there is such a smoke.

If you use some other method of measuring current--break
circuit and
insert ammeter, or use clamp-on-meter, the meter will tell
you there's a
short, all right, at about the same time the transformer
erupts in a
ball of smoke and fire.


--
The current state of literacy in our advanced civilization:

yo
wassup
nuttin
wan2 hang
k
where
here
k
l8tr
by

- from Usenet (what's *that*?)

On 4/11/2011 9:31 PM, John Robertson wrote:
Tony Miklos wrote:
On 4/9/2011 10:06 PM, John Robertson wrote:
Steve Turner wrote:
On 4/9/2011 7:29 PM, Jim Yanik wrote:
wrote in
m:

"Steve Turner" wrote in message ...

A continuation of the "Why does the 115V-24V transformer keep
blowing on my Trane XB80?" discussion I started on 04/02/2011.

Yep, My A/C unit blew another transformer. Pictures (and wiring
diagram) he

http://www.flickr.com/photos/bbqboye...7626457562742/

Trane's manual for the unit is here (for perhaps better viewing of
the wiring diagrams that I also copied to my above flickr site as
jpg images):



http://www.trane.com/webcache/un/fur...oduct/22-1666-

07_04012009.pdf

As you can probably see in the pictures, there is visible charring
of the 115V leads going into the transformer, and of course the 115V
circuit is open (again). If you didn't see my first thread, this is
the third transformer the unit has blown. In the previous
discussion, it was discussed that perhaps the first one just blew
because of old age (6 years), and the second blew because it wasn't
a proper replacement (poor quality, made in China, etc.). This
third unit is most certainly a proper replacement, and it's most
certainly indicative of a real problem I have somewhere else in the
unit. I didn't see any such charring on the previous two units, at
least not like this.

I never got a real chance to test out the system after installing
this third transformer. We had cool weather for several days, and I
never tried to force the system to come on so I could monitor it;
that was probably a mistake. Unfortunately, I was also absent from
the premises during the extended times when the unit was most likely
operational, so that didn't help either. However, my family tells me
that it WAS working and cooling the house rather nicely, for at
least a day, perhaps two. I'm getting 115V in all the right places,
so it doesn't look like an over-voltage condition to me. Perhaps
it's an overheating condition? It looks to me like the only real
load on this circuit is the blower motor; could the motor be causing
this? The blower spins freely when I turn it by hand. Start
capacitor on the motor maybe? Relay on the control board perhaps?

a bad start cap would not affect the 24v control transformer,that just
powers the controller board and relays.
either something is loading the transformer or a problem with input
voltage.


Just a thought,

When you put the new transformer in does the "Diagnostic Light" LED
turn on ?
Does the LED blink or flash in one of the patterns indicated in the
"diagnostic codes" section that you posted a link to ?

The "diagnostic codes" imply that the control board can detect
several of the problems mentioned by others.
Maybe a good starting point as there is not enough time to test with
test equipment.

robb



a line voltage monitor may be needed to see if there's some short-term
overvoltage applied to the transformer,and a oscilloscope may
determine if
the input waveform is sinusoidal or otherwise,because 60hz iron core
tranformers don't like extreme distortion on their input,it gets
converted
to heat,not output voltage. a DMM will not show line distortion or
short
term overvoltages.
are the wires burned close to the transformer,or over their entire
length?

I peeled the insulation back from the hot and neutral wires and the
burning only occurred right at the terminals, no more than 1/4" into
the wiring.


So the problem is the joint of the transformer wiring to the lugs. They
may have cold solder joints, or the lug may be slightly loose - enough
to crack the solder connection over time. Your transformer may still be
good!

When you are examining the transformer wire make sure it is stripped
enough to get good solder coverage. Burn off the insulation (enamel) -
do not sand, scrape, or try to erode it because if you scratch the wire
it will break at the scratch.

Re-solder the transformer connectors after first making sure the wire
has at least two complete wraps around the solder lug and the solder
makes a good meniscus joint to the wire and lug. Also use a good grade
of solder, not regular 60/40, find some 63/37 solder (Kester is best) -
this solder resists cold solder joints due to movement when cooling by
solidifying very fast.

John :-#)#

Hi John, fancy meeting you here! Wait, I didn't realize this is cross
posted to sci.electronics.repair Now I know why you are here. Glad you
liked the package.

Tony

Hi Tony,

Yes, we enjoyed the peanut brittle...

I do not think the original poster noticed my suggestion above, that
failure mode is really not going to be too much load or some weird AC
situation - it's either a short to the metal case the transformer is
mounted in or a problem with the wire to solder lug joint.

Would be nice to know if that idea was checked out...

John :-#)#

Yes, the thread got too long. If you saw the photo, and know the
primary went open on 3 transformers, it sure looks like a problem on the
primary side. If the load was too much, those wires on the secondary
side would most likely have been at the very least discolored from the heat.

Tony

On 4/11/2011 7:26 PM, Don Klipstein wrote:
, Jeff Thies wrote:

SNIP to getting a nonpolarized 1uF cap suitable for 120 VAC

If not then go buy a 200V non polarized 1uF cap. It is no easy chore.

http://search.digikey.com/scripts/Dk...dll?Cat=131081

200V DC rating is not enough, despite 120 VAC having a peak voltage
of only 169 volts.

AC does make things worse, by rapidly repeated severe voltage swings
combined with some development of heat.

The capacitor needs to have an actual AC rating, and one that includes
your AC voltage with a comfortable safety margin. If it has a DC rating,
chances are that will be around 400 volts DC. And not every cap rated
400 VDC is dsafe for use with 120 VAC, even if non-polarized.

Preferably, it should be "UL recognized" or the like, for some assurance
that it is reasonably reliable against failure, or at least an unsafe
failure.

Back in the early 1980's, in an experimental sodium lamp ballast, I have
blown an 800VDC cap and two 600 VDC ones with 240-260 VAC 60 Hz with less
than 10 operating hours of this combined among the three of them. One of
those capacitor blowups was a spectacular one that left a major oil stain
on the ceiling above. I learned the hard way that actual AC ratings are
required here.

Yes, many moons ago I was playing with adding a mylar cap in series with
the primary of a neon sign transformer. It worked great for making the
neon dimmer which was my attempt, but I recall measuring a much higher
voltage across the cap due to the reactence and impedence of them in
series. I'm guessing but I think it was up in the 400vac or so range
maybe higher. Not good for the transformer winding either. I didn't
blow them but stopped using them after reading the voltages.

On 4/11/2011 2:27 PM, David Nebenzahl wrote:
On 4/11/2011 6:27 AM Tony Miklos spake thus:

On 4/11/2011 12:59 AM, wrote:

On Sun, 10 Apr 2011 00:18:44 -0400, Jeff
wrote:

On 4/9/2011 9:41 PM, wrote:

On Sat, 09 Apr 2011 19:22:57 -0400, Jeff
wrote:

But first do as I suggested in another thread,look carefully
for anything burnt and check the polarity of the line. Make
sure the neutral is neutral. You can measure from the ground
prong. See the note in the schematic. I'm not so sure this
didn't arc to the transformer shell, from looking at the pic.
You may wish to measure voltage (AC) from the transformer
shell to a guaranteed neutral.

It's AC so there is no polarity. It's single output, non
grounded, so it doesnt matter which direction either the
primary or secondary are connected. Good to have the white on
neutral and the bloack on live, but it will have NO EFFECT on
the operation. - or the life of the transformer.


Except that the schematic has a note at the top that says:

Important
Integrated Control is polarity sensitive. Hot leg of 120V power
supply must be connected to the black power lead...

Whats with that?

I'm sure I am as baffled by that as you are. AC in not "polarity
sensitive" and as long as neither side of the primary or secondary
is grounded the control should not know which way the primary (or
secondary) is connected..

I have a guess, maybe the board has to be in sync with another power
source. Would reversed polarity make it 180º out of sync?

Now you're *really* grasping at straws ...


I am because I don't know why else it would have to be polarized.

On Tue, 12 Apr 2011 17:37:15 +1000, "Phil Allison"
wrote:



Got a ****ing clue how much current it takes to vaporise copper wires like
that ?

Obviously ****ing not.

How about "more than 15 amps"?

And it didn't blow the circuit breaker or fuse.
So the current came from somewhere other than the mains?
OK - the only other source is back emf from the motor -
Not saying it cannot be.
But why does the insulation on the transformer fail, and not the
insulation in the motor windings??
Most likely, if your scenario is correct, because there is something
wrong with the quality of the transformer windings.

And what is the solution????? Other than a transformer that can stand
up to real world abuse?
Find and repair the power connection problem that is causing the
back-emf problem before it causes other problems (like a fire from an
overheated power connection to a 1/2 HP motor)

NOT by putting a capacitor which may or may not have any effect across
the primary of the transformer. And MAY have the wrong effect.

Now, you need to locate the bad connection (if that is what it is)
Where do you start looking? It pretty well needs to be in the part of
the circuit that is always connected to both the motor and the
transformer - in other words upstream from wherever the transformer
and motor are connected (in common) to the mains, or else the back emf
would be "sunk" by the load on the mains, and the grid itself. - so
you are talking bad breaker, bad connection at the panel, bad shut-off
switch, or bad connections between the panel and the switch - not bad
relays, connections at the relays, or connections at or in the motor.

You would THINK there would be other symptoms - like the furnace
intermittently not running, noises, smoke, etc from the arcing
connection?

Again, not saying you are wrong - but you are not being very helpfull,
and you are sure being obstinate and dissagreeable

Facts are just like water off a duck's back to you - Don.

Cos ****wits like you believe whatever they ****ing feel like.


FOAD

- you useless, autistic, PITA turd.



.... Phil

Tony Miklos wrote:
On 4/11/2011 9:31 PM, John Robertson wrote:
Tony Miklos wrote:
On 4/9/2011 10:06 PM, John Robertson wrote:
Steve Turner wrote:
On 4/9/2011 7:29 PM, Jim Yanik wrote:
wrote in
m:

"Steve Turner" wrote in message ...

A continuation of the "Why does the 115V-24V transformer keep
blowing on my Trane XB80?" discussion I started on 04/02/2011.

Yep, My A/C unit blew another transformer. Pictures (and wiring
diagram) he

http://www.flickr.com/photos/bbqboye...7626457562742/

Trane's manual for the unit is here (for perhaps better viewing of
the wiring diagrams that I also copied to my above flickr site as
jpg images):



http://www.trane.com/webcache/un/fur...oduct/22-1666-


07_04012009.pdf

As you can probably see in the pictures, there is visible charring
of the 115V leads going into the transformer, and of course the
115V
circuit is open (again). If you didn't see my first thread, this is
the third transformer the unit has blown. In the previous
discussion, it was discussed that perhaps the first one just blew
because of old age (6 years), and the second blew because it wasn't
a proper replacement (poor quality, made in China, etc.). This
third unit is most certainly a proper replacement, and it's most
certainly indicative of a real problem I have somewhere else in the
unit. I didn't see any such charring on the previous two units, at
least not like this.

I never got a real chance to test out the system after installing
this third transformer. We had cool weather for several days, and I
never tried to force the system to come on so I could monitor it;
that was probably a mistake. Unfortunately, I was also absent from
the premises during the extended times when the unit was most
likely
operational, so that didn't help either. However, my family
tells me
that it WAS working and cooling the house rather nicely, for at
least a day, perhaps two. I'm getting 115V in all the right places,
so it doesn't look like an over-voltage condition to me. Perhaps
it's an overheating condition? It looks to me like the only real
load on this circuit is the blower motor; could the motor be
causing
this? The blower spins freely when I turn it by hand. Start
capacitor on the motor maybe? Relay on the control board perhaps?

a bad start cap would not affect the 24v control transformer,that
just
powers the controller board and relays.
either something is loading the transformer or a problem with input
voltage.


Just a thought,

When you put the new transformer in does the "Diagnostic Light" LED
turn on ?
Does the LED blink or flash in one of the patterns indicated in the
"diagnostic codes" section that you posted a link to ?

The "diagnostic codes" imply that the control board can detect
several of the problems mentioned by others.
Maybe a good starting point as there is not enough time to test with
test equipment.

robb



a line voltage monitor may be needed to see if there's some
short-term
overvoltage applied to the transformer,and a oscilloscope may
determine if
the input waveform is sinusoidal or otherwise,because 60hz iron core
tranformers don't like extreme distortion on their input,it gets
converted
to heat,not output voltage. a DMM will not show line distortion or
short
term overvoltages.
are the wires burned close to the transformer,or over their entire
length?

I peeled the insulation back from the hot and neutral wires and the
burning only occurred right at the terminals, no more than 1/4" into
the wiring.


So the problem is the joint of the transformer wiring to the lugs. They
may have cold solder joints, or the lug may be slightly loose - enough
to crack the solder connection over time. Your transformer may still be
good!

When you are examining the transformer wire make sure it is stripped
enough to get good solder coverage. Burn off the insulation (enamel) -
do not sand, scrape, or try to erode it because if you scratch the wire
it will break at the scratch.

Re-solder the transformer connectors after first making sure the wire
has at least two complete wraps around the solder lug and the solder
makes a good meniscus joint to the wire and lug. Also use a good grade
of solder, not regular 60/40, find some 63/37 solder (Kester is best) -
this solder resists cold solder joints due to movement when cooling by
solidifying very fast.

John :-#)#

Hi John, fancy meeting you here! Wait, I didn't realize this is cross
posted to sci.electronics.repair Now I know why you are here. Glad you
liked the package.

Tony

Hi Tony,

Yes, we enjoyed the peanut brittle...

I do not think the original poster noticed my suggestion above, that
failure mode is really not going to be too much load or some weird AC
situation - it's either a short to the metal case the transformer is
mounted in or a problem with the wire to solder lug joint.

Would be nice to know if that idea was checked out...

John :-#)#

Yes, the thread got too long. If you saw the photo, and know the
primary went open on 3 transformers, it sure looks like a problem on the
primary side. If the load was too much, those wires on the secondary
side would most likely have been at the very least discolored from the
heat.

Tony

Yes, I looked at the pictures (rather poor resolution). The failure
looks like a connection issue because there is no evidence of windings
overheating. If the output was shorted the transformer would burn up -
assuming it could sink enough current, but it would be unlikely to flare
at one spot. This is a pretty standard 115VAC transformer, I've seen
many of them...

If someone tried to pump 5000 volts into the transformer then possibly
you could get an arc like that to the transformer frame, so that would
mean a serious miss-wiring of the furnace where the igniter somehow was
connected to the primary of the transformer and then turned on.

Hard to see that happening as the transformer powers the logic board
that would enable the igniter to fire up!

John :-#)#

--
(Please post followups or tech enquiries to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

On Mon, 11 Apr 2011 23:07:50 -0400, Jeff Thies wrote:

On 4/11/2011 10:01 PM, wrote:
On Tue, 12 Apr 2011 00:12:48 +0000 (UTC), (Don
Klipstein) wrote:

In , Jeff Thies wrote:
On 4/11/2011 11:25 AM, Smitty Two wrote:
In ,
Jeff wrote:

My first encounter with you

Jeff, since you don't hang out on s.e.r., I'll clue you in about
Phil. Regardless of what he knows or doesn't know, he calls everyone
a ****wit, and worse, all the time. Virtually every sentence of
every post is chock full of derision. If you choose to dialogue with
him, you'll get great heaping portions of his demented abuse. So
don't take it personally.

Thanks. That's about what I surmised. A North American version of
Rod
Speed.

I think Rod Speed is much worse. Meanwhile, it appears to me in my
experience in s.e.d. that P.A. is, like R.S., an Aussie.
That would go a long ways to explaining his potty mouth.

Perhaps that goes all the way. Hey, I learned something about Oz today.
Funny the guys from NZ I know seem quite nice. I suppose it was a surly
lot they are descended from... or is it the climate? No matter.

Jeff

A friend traveled to NZ then to OZ in 2004. He said when he got off the
plane in NZ he thought the pilot had landed in China because 99% of the
people around were Asian. I have relatives living near Sidney and they
said this isn't the case there.



--
Live Fast Die Young, Leave A Pretty Corpse

On 4/12/2011 2:38 AM Stormin Mormon spake thus:

There you go, again. Completely mistaken about what I'd
reccomend in the way of diagnostic. Just making up garbage,
and then trying to assign it to me. Well, you should do that
more often. Then, everyone can see what your true character
is like. Please write often, and lengthy. The more you
write, the better I look.

In your mind, perhaps.


--
The current state of literacy in our advanced civilization:

yo
wassup
nuttin
wan2 hang
k
where
here
k
l8tr
by

- from Usenet (what's *that*?)

On 4/12/2011 8:10 AM Tony Miklos spake thus:

On 4/11/2011 2:27 PM, David Nebenzahl wrote:

On 4/11/2011 6:27 AM Tony Miklos spake thus:

On 4/11/2011 12:59 AM, wrote:

I'm sure I am as baffled by that as you are. AC in not
"polarity sensitive" and as long as neither side of the primary
or secondary is grounded the control should not know which way
the primary (or secondary) is connected..

I have a guess, maybe the board has to be in sync with another
power source. Would reversed polarity make it 180º out of sync?

Now you're *really* grasping at straws ...

I am because I don't know why else it would have to be polarized.

Well, it *is* a mystery ...


--
The current state of literacy in our advanced civilization:

yo
wassup
nuttin
wan2 hang
k
where
here
k
l8tr
by

- from Usenet (what's *that*?)

In , wrote:
On Tue, 12 Apr 2011 17:37:15 +1000, "Phil Allison"
wrote:

Got a ****ing clue how much current it takes to vaporise copper wires like
that ?

Obviously ****ing not.

How about "more than 15 amps"?

And it didn't blow the circuit breaker or fuse.
So the current came from somewhere other than the mains?

I don't remember any V-A rating stated for the tranny in question since
the number of posts in the 2 threads is huge. Though, I have the
impression it's around 40 or 50 or so.

A 120V one this size usually has its primary around AWG 24 or 26, and a
240V one or a dual-primary 120/240V one usually has primary winding size
around AWG 28. Properly connected for 120V, that means 2 roughly-AWG-28
strands in parallel, effectively around AWG 25.

A transformer winding this size can gradually get charring hot at as
little as 1 or 1.5 amps or so.

Leads of this size get charring hot within a minute at several amps.

The CRC Handbook says fusing current for copper wire is 20 amps for AWG
26, 30 amps for AWG 24. Though these figures are only approximate, I
usually hear that these fusing current charts are for bare wire in free air.
Fusing current will be less for a wire next to another turn of overheating
wire.

Meanwhile, I doubt a 15 amp slow-blow fuse or slow-acting breaker will
keep a 26 or 24 AWG wire from fusing. One thing to keep in mind is that a
15 amp fuse or breaker normally passes 15 amps without opening, and may
take a few seconds or more to open at 20 amps.

I think the overcurrent that caused charring here came from the power
line without opening the breaker/fuse. Back EMF won't do that, though it
could cause insulation failure. However, I doubt that explains 3 blown
transformers and nothing else blown.

--
- Don Klipstein )

In article , Tony Miklos wrote:

Yes, the thread got too long. If you saw the photo, and know the
primary went open on 3 transformers, it sure looks like a problem on the
primary side. If the load was too much, those wires on the secondary
side would most likely have been at the very least discolored from the
heat.

This makes me think the most likely causes a

* Improperly connecting the transformer (such as using only 1 of the 2
primaries of a 120/240V dual primary transformer)

* DC flowing through the secondary. That can occur if the tranny's load
has a fullwave rectifier with one diode open. If the fullwave
rectifier has discrete diodes or a dual diode, the problem may be a bad
solder joint at one of the diodes.

DC through the secondary is well known to be able to cause transformer
cores to saturate. That can lead to the primary drawing excessive
current.

* Less likely - there is a magnet on the transformer core. That
combined with the tranny's normal magnetic flux can cause core
saturation, similar to the effect of DC in a winding although this
usually only causes part of the core to saturate.

However, a magnet on the core appears to me "probably unlikely to be
an actual problem" unless the tranny is of marginal design, line voltage
is on the high side, or the magnet is especially powerful.

There is the matter of voltage spikes on the primary blowing the
insulation. However, I consider that unlikely if nothing else has been
blown while 3 transformers blew.

--
- Don Klipstein )

Don Klipstein wrote:
In article , Tony Miklos wrote:

Yes, the thread got too long. If you saw the photo, and know the
primary went open on 3 transformers, it sure looks like a problem on
the primary side. If the load was too much, those wires on the
secondary side would most likely have been at the very least
discolored from the heat.

This makes me think the most likely causes a

* Improperly connecting the transformer (such as using only 1 of
the 2 primaries of a 120/240V dual primary transformer)

* DC flowing through the secondary. That can occur if the tranny's
load has a fullwave rectifier with one diode open. If the fullwave
rectifier has discrete diodes or a dual diode, the problem may be a
bad solder joint at one of the diodes.


That's not true. an open rectifier does not allow DC current to flow
through the secondary. It's just 1/2 of the power line cycle. During the
opposite half of the cycle, no current flows in the secondary. True, it's
unidirectional current, but it's an intermittent current, not constant DC.
If your statement were true, then half-wave rectifiers wouldn't be feasible.

--
David
dgminala at mediacombb dot net

"Dave M"


That's not true. an open rectifier does not allow DC current to flow
through the secondary. It's just 1/2 of the power line cycle. During the
opposite half of the cycle, no current flows in the secondary.

** So the average value is non zero and that means there is a DC component
to the current.

True, it's unidirectional current, but it's an intermittent current, not
constant DC.

** It will show a nice, steady reading on a DC current meter.

The interesting thing is how there is no corresponding DC component in the
primary current.


..... Phil

Stormin Mormon wrote:

OK, that makes a bit of sense. Seems like a bit of bother
for what you can track down, with a VOM and some common
sense.


The 'Dimbulb tester' will show a transformer that is in saturation,
or one that has a shorted turn. Your VOM can't.


--
You can't fix stupid. You can't even put a Band-Aid™ on it, because it's
Teflon coated.

In article , Dave M wrote:
Don Klipstein wrote:
In article , Tony Miklos wrote:

Yes, the thread got too long. If you saw the photo, and know the
primary went open on 3 transformers, it sure looks like a problem on
the primary side. If the load was too much, those wires on the
secondary side would most likely have been at the very least
discolored from the heat.

This makes me think the most likely causes a

* Improperly connecting the transformer (such as using only 1 of
the 2 primaries of a 120/240V dual primary transformer)

* DC flowing through the secondary. That can occur if the tranny's
load has a fullwave rectifier with one diode open. If the fullwave
rectifier has discrete diodes or a dual diode, the problem may be a
bad solder joint at one of the diodes.


That's not true. an open rectifier does not allow DC current to flow
through the secondary. It's just 1/2 of the power line cycle. During the
opposite half of the cycle, no current flows in the secondary. True, it's
unidirectional current, but it's an intermittent current, not constant DC.
If your statement were true, then half-wave rectifiers wouldn't be feasible.

A unidirectional pulsing waveform has a DC component.

That analyzes to a sum of DC, fundamental frequency AC, and AC at
harmonic frequencies. The average as averaged over a whole cycle is the
DC component.

It is fairly well known that a transformer driving a halfwave rectified
load can run into core saturation problems from the DC component in the
unidirectionally pulsing current waveform.

--
- Don Klipstein )

On Wed, 13 Apr 2011 09:57:33 +1000, "Phil Allison"
wrote:


"Dave M"


That's not true. an open rectifier does not allow DC current to flow
through the secondary. It's just 1/2 of the power line cycle. During the
opposite half of the cycle, no current flows in the secondary.

** So the average value is non zero and that means there is a DC component
to the current.

True, it's unidirectional current, but it's an intermittent current, not
constant DC.

** It will show a nice, steady reading on a DC current meter.

The interesting thing is how there is no corresponding DC component in the
primary current.


.... Phil

Unless the half wave rectifier is on the PRIMARY side.
I don't see any evidence of that on any of the diagrams I saw, but is
there something else on this furnace circuit? By code there cannot be
- but we don't know know this to be the case - or what is on the
circuit if there is.

To the OP...
another long shot..

it looks like the primary of the transformer is wired in series with
the door safety switch. Is it possible that the door safety switch
is loose and arcing. This could cause a high voltage to appear at the
transformer and cause the insulation to fail...


Mark

Phil Allison wrote:
"Dave M"


That's not true. an open rectifier does not allow DC current to flow
through the secondary. It's just 1/2 of the power line cycle. During the
opposite half of the cycle, no current flows in the secondary.

** So the average value is non zero and that means there is a DC component
to the current.

True, it's unidirectional current, but it's an intermittent current, not
constant DC.

** It will show a nice, steady reading on a DC current meter.

The interesting thing is how there is no corresponding DC component in the
primary current.


.... Phil

Hi,
Lots of ripple. If it were on audio circuit, lots of hum!!!!

In article , HeyBub wrote:

SNIP to malevolance of machines, not just furnaces

I've seen malevolent machines. I've been victimized by our metal overlords.

Tell the truth, have you never been tempted to shotgun a lawnmower?

http://www.ssiworld.com/watch/lawn-mower.htm


Linked from http://www.watchitshred.com

That place even shows shredding of some engine blocks. They make
shredding of bowling balls look easy!

Is a computer or some other electronic device ticking you off?
http://www.ssiworld.com/watch/e-scrap.htm

They even shred shredders:
http://www.ssiworld.com/watch/shredder.htm

--
- Don Klipstein )

In , wrote:
On 13 Apr 2011 09:57:33 +1000, "Phil Allison" wrote:

"Dave M"

That's not true. an open rectifier does not allow DC current to flow
through the secondary. It's just 1/2 of the power line cycle. During the
opposite half of the cycle, no current flows in the secondary.

** So the average value is non zero and that means there is a DC component
to the current.

True, it's unidirectional current, but it's an intermittent current, not
constant DC.

** It will show a nice, steady reading on a DC current meter.

The interesting thing is how there is no corresponding DC component in the
primary current.

.... Phil

Unless the half wave rectifier is on the PRIMARY side.

There won't be a rectifier feeding the primary of a transformer with DC.
A transformer does not pass DC from one winding to another the way it does
with AC.

Changing AC that transformers work with to DC that electronics work with
has to occur downstream of the transformer.

I don't see any evidence of that on any of the diagrams I saw, but is
there something else on this furnace circuit? By code there cannot be
- but we don't know know this to be the case - or what is on the
circuit if there is.

I have yet to look at these diagrams, but is the circuit board
powered by this tranny shown to "board level" as opposed to "component
level"? If so, then the board can have, probably does have, a rectifier
not shown in the diagram.
--
- Don Klipstein )

On 4/12/2011 9:23 PM Don Klipstein spake thus:

I have yet to look at these diagrams, but is the circuit board
powered by this tranny shown to "board level" as opposed to "component
level"? If so, then the board can have, probably does have, a rectifier
not shown in the diagram.

With all the pontificating you've been doing here, Don, I would've
thought you'd at least had glanced at the wiring diagrams the OP posted,
way up there somewhere. Sheesh.

The controller is shown as a block. It most certainly has at least one
rectifier on it, as it contains electronics that no doubt requires DC
power to operate. Thought you'd have figured it out. (Not just a relay
board.)


--
The current state of literacy in our advanced civilization:

yo
wassup
nuttin
wan2 hang
k
where
here
k
l8tr
by

- from Usenet (what's *that*?)

On 4/12/2011 11:12 PM, Don Klipstein wrote:
In articleOr6dneUjdf0znTjQnZ2dnUVZ_i2dnZ2d@earthlink .com, HeyBub wrote:

SNIP to malevolance of machines, not just furnaces

I've seen malevolent machines. I've been victimized by our metal overlords.

Tell the truth, have you never been tempted to shotgun a lawnmower?

http://www.ssiworld.com/watch/lawn-mower.htm


Linked from http://www.watchitshred.com

That place even shows shredding of some engine blocks. They make
shredding of bowling balls look easy!

Is a computer or some other electronic device ticking you off?
http://www.ssiworld.com/watch/e-scrap.htm

They even shred shredders:
http://www.ssiworld.com/watch/shredder.htm


Having an extremely warped mind, I thought some Hollywood special
effects guys should get together with a shredder company and make
a very special YouTube video of an Islamic terrorist being tied up
in a big burlap sack with a hog. The whole squirming mass would be
dropped into a monster shredder and all the sound effects, blood
and guts would be awesome. At the end, a disclaimer would read....
"No actual pigs were harmed during the production of this video"
Of course the reaction would be the same as the nut-jobs who were
upset about their Koran being burned and went around killing everyone
they could find who they believed to be a Christian.

TDD